Melatonin — the pineal gland’s signal for darkness and sleep initiation — is the world’s most studied sleep supplement and one of the few with consistent evidence across multiple sleep disorders. Its role is primarily circadian: it tells the body when to sleep, not how deeply.
What Does the Research Say?
A 2013 Cochrane review of 19 randomized trials found melatonin significantly reduced sleep onset latency by an average of 7 minutes and increased total sleep time by 8 minutes compared to placebo — modest but consistent. For jet lag, the evidence is more compelling: a Cochrane review of 10 trials found melatonin highly effective for reducing symptoms when taken at the destination local bedtime. The dose-response relationship is counter-intuitive: 0.5mg is as effective as 3–5mg for most people, as endogenous melatonin levels peak at just 0.3–0.5mg equivalent.
Melatonin’s primary utility is circadian phase shifting rather than sedation — it works best for delayed sleep phase disorder, shift work, and jet lag rather than insomnia proper. For children, pediatric studies show consistent benefit for sleep-onset insomnia particularly in autism spectrum disorder (ASD) and ADHD populations. A 2020 meta-analysis confirmed melatonin reduced sleep latency in children by ~29 minutes with no serious adverse effects. Extended-release formulations better maintain levels through the night for sleep maintenance issues.
Key Findings
- Cochrane review: melatonin reduces sleep onset latency by ~7 minutes and increases total sleep time
- Strong evidence for jet lag — most effective sleep intervention for circadian desynchrony
- 0.5mg is as effective as 5mg for most adults — supraphysiological doses likely counterproductive
- Particularly effective in children with ASD and ADHD — reduces sleep latency by ~29 minutes
Practical Takeaway
Take 0.5–3mg melatonin 30–60 minutes before desired sleep time. Higher doses do not improve sleep quality and may cause next-day grogginess. Use for 2–4 weeks for acute use cases (jet lag, schedule shifts); for chronic insomnia, address root causes with sleep hygiene and CBT-I rather than indefinite melatonin. Find melatonin: melatonin supplements.